Multilayer wiring structures have been adopted to realize the high integration of semiconductor devices. Here, as for the interlayer insulating film for insulating between each layer, it is required to decrease the relative permittivity in order to further increase the speed of device operations. Based on such a request, a fluorine added carbon film (fluorocarbon film), that is a compound of carbon (C) and fluorine (F) has been considered to be adopted as the interlayer insulating film. In the fluorine added carbon film, for example, the relative permittivity can be maintained to 2.5 or below, if the type of material gas is selected. That is, the fluorine added carbon film is an extremely effective film as an interlayer insulating film.
Meanwhile, the fluorine added carbon film is an organic film. Thus, in an etching process, the gas for etching the fluorine added carbon film also etches a resist film, which is an organic material, at the same time. For this reason, when the fluorine added carbon film is used as an insulating film, a thin film for hard mask that functions as a mask at the etching (aside from the resist film), is required to be laminated on the fluorine added carbon film. A SiO2 film, or the like is known as a material of the thin film for hard mask.
The Japanese Unexamined Patent Application Publication No. 2005-302811 discloses a technique to combine a SiO2 film and an oxygen added silicon carbide (SiCO) film with a low relative permittivity as a thin film for hard mask in order to suppress the increase of the relative permittivity in the entire interlayer insulating film. This SiCO film is, for example, a silicon carbide film which contains oxygen about 20 atomic %.
At this time, the inventors of the application considered to form a film that contains silicon, carbon and nitrogen (hereinafter referred as “SiCN film”) layer between the fluorine added carbon film and a thin film for hard mask as a barrier layer in order to prevent the fluorine in the fluorine added carbon film from moving to the thin film for hard mask. The reason for using the SiCN film as a barrier layer here is that in a thin film having a bond of silicon and oxygen (Si—O bond), it is necessary to use the barrier layer that does not contain the bond because the Si—O bond is cut by a fluorine when the fluorine of the fluorine added carbon film enters into the film, and as a result the fluorine moves to the hard mask layer side.
By the way, when forming a SiCN film and a thin film for the hard mask on the fluorine added carbon film, for example, first the SiCN film is formed on the fluorine added carbon film using the plasma CVD (Chemical Vapor Deposition) by plasmanizing a trimethylsilane gas and an ammonia gas. Next, a SiCO film is formed on the SiCN film by plasmanizing the gas containing silicon, carbon and oxygen. Thereafter, a SiO2 film is formed on the SiCO film by plasmanizing the gas containing silicon and oxygen.
However, when the SiCN film, SiCO film, and SiO2 film are formed on the surface of the fluorine added carbon film according to such a process, a large amount of fluorine from the fluorine added carbon film enters into the SiCN film during these film forming processes. Thus, there is a possibility for the fluorine in the SiCN film to penetrate through the SiCN film when heated and the fluorine moves to the interface of the hard mask layer and the SiCN film during, for example, a hydrogen annealing process, in which a heat treatment at 400 degree/C is performed, after an integrated circuit is manufactured, or a heat treatment process while manufacturing an integrated circuit. And, in a case when the fluorine concentration on the interface is high, the hard mask layer peels off from the SiCN film, and this force of peeling off may result in a problem of wire breakage in a copper wiring layer.
Here, in a case when the forming process temperature for the fluorine added carbon film is high, about 380 degree/C, the amount of the fluorine scatter from the fluorine added carbon film when forming a film is large. Therefore, at the forming process of SiCN film, SiCO film, SiO2 film or the like, the amount of fluorine entering into the SiCN film is relatively small, and the amount of fluorine moving to the interface of the hard mask layer and SiCN film is relatively small, thereby the film peeling of the hard mask layer is less likely to occur.
However, based on the request for attempting to reduce the total relative permittivity of the film in the semiconductor devices, there has been a demand for further decreasing the heat quantity for the overall manufacturing process of the semiconductor device. Accordingly, it has been considered to perform the film forming process for the fluorine added carbon film at the temperature about 345 degree/C. Because the large amount of fluorine remains in the fluorine added carbon film formed at such a temperature, as a result, the amount of fluorine entering into the SiCN film increases when forming the SiCN film, SiCO film and SiO2 film, and the film peeling of the hard mask layer is likely to occur, which may lead to a problem.